Gas Mileage with 235s

Guys, I did a search and couldn't find any comment on the mileage and drivability of the third gen with 235 tires. I am specifically looking for mileage concerning 235/80R17 with all other items stock. Any input of experiences, mileage, and pictures would be much appreciated!

Thank you in advance

 

Not sure on MPG but those would cut up my pizza I had for lunch quite nicely

 

They're 32" LT tires, so MPG will be comparable to any other 32's. The width really has no significant bearing on MPG.

 

Might be a little better because they should be lighter. Rotating mass is a big deal.

 

On my 4runner, I just went to a slightly taller, but lighter and smoother tire, and MPG went up significantly.

 

It's not that much different. It's a 5lb difference between the two. But remember, 235's are slightly taller as well. My experience has been, no difference. (Given same tire).

 

Can't really say "any other 32" as tire weights vary considerably, one 32 might weight 40lbs while another one the exact same size will be 55lbs.

Also width absolutely effects mpg which is why EVs and hybrids all ride on skinny LRR tires, because more contact patch = more rolling resistance.

I do agree that the greater effect will be from tire weight, a heavy 235 will probably have worse mpg that a particularly light 265.

 

Contact patch is the same size no matter what size tire you run, it just changes shape. Overriding factor is inflation pressure and weight on the axle, and then tire carcass stiffness follows that.

Skinny tires displace less air and weigh less, hence they have the potential for using less fuel.

I doubt that OP would notice any significant changes to MPG from going to 235/80s.

 

Again, I've run both. 235 and 265. No difference. We're talking 30mm, or about an inch of difference here. Look at the frontal area of your truck. That is miniscule.

Weight is certainly a factor, but when you're talking 32's L/T (I specified L/T in the original post), I don't know of a 235/80/17 tire that weighs 40lbs. All are high 40's or 50's. Same as 265's.

 

I just went from 275/65/18 tires which are 50lbs each and 32.1" diameter to 265/70/18 at 44lbs and 32.6" diameter and got over 2 mpg difference on the trip computer over the same commute. I'm sure it also has a lot to do with tread pattern, but 5-6lbs per tire is not insignificant.
So as always YMMV

 

Geez we just had a huge scientific discussion in two other threads that completely debunks that. a 33/12.5 will have a larger contact patch than a 33x10.5 for example. I have the damn ink blotches on my garage floor to prove it.

 

Yeah I know everyone thinks that but they're also wrong. It will have a wider contact patch, not a larger one.

 

Again we already had this discussion. The same tire, same load, same everything except width, the tire contact length remains the same but the width is different thus a larger contact patch. 7" x 8" vs 7" x 10.5" LxW = A

 

So from what I've been able to figure out, the whole skinny vs fat contact patch kinda lands in the middle.

Basically, in an idealized scenario area would be dependant only on load and tire pressure. BUT in reality, the way tires are built (semi rigid) means this usually isn't the case.

Generally a wider tire will have a larger contact patch, but not proportionally to the difference in width. As the tire gets wider, the length of the patch does decrease but not at the same rate.

It also appears that the relationship is highly dependent on what tire pressure you are comparing at. At some pressures the skinny and wide will have the same patch, at others the wider will be slightly bigger. I don't recall that the skinny ever has a bigget patch.

As far as OPs question, I'm curious as well. I'm thinking it'd be better on gas, for my next tire I'm planning on Cooper AT3 but I'm torn between the 265/75/16 4s at 41lbs and 235/85/16 LT at 43lbs.

 

Area is determined by load (F) and ground pressure (P) Since P =F/A, A = F/P. The problem is people confuse P with tire pressure and in reality P is ground pressure. As A increase P decreases, thus a larger contact patch reduces ground pressure.

 

Very good point. The two pressures are obviously related, as a high tire pressure will result in small contact patch and higher ground pressure, and vice versa.

As for the actual math and such for the relationship...

That's above my pay grade lol.

 

Definitely and you are right there is a tire pressure between the two to have equal contact patch but not sure what that it.

I don't know the relational math either but I do know that the tire contact patch can't be calculated with tire pressure directly. We discovered that the ground pressure on a stock tire was about 25 psi but they were inflated to 32psi.

The only way we could make any real conclusion was, I had to spray paint my tire, drop it down and measure the contact area lol. I actually got that idea from an Army manual as that is how they measure ground pressure. They take ink measurments

 

It sounds like a lot of my theories are the norm around here. I was hopeful for someone with experiences on a third gen because I am also wondering how the motor/AT tranny will behave with the more narrow/taller tire. I appreciate everyone chiming in on this and maybe I will just have to be the guinea pig on this.

 

@ccallen

 

(not a 3rd gen) but I had some on my '06 RC 4x4 (KO2 E range) They were heavy and dropped my mileage a bit, but they looked great to me!